1. Field of the Invention
Exemplary aspects of the present invention relate to a development device and an image forming apparatus, and more particularly, to a development device and an image forming apparatus for efficiently agitating a two-component developer.
2. Description of the Related Art
A related-art image forming apparatus, such as a copier, a facsimile machine, a printer, or a multifunction printer having at least one of copying, printing, scanning, and facsimile functions, typically forms a toner image on a recording medium (e.g., a transfer sheet) according to image data using electrophotography. Thus, for example, in a typical electrophotographic image forming process, a charging device charges a surface of a latent image carrier; an optical writer emits a light beam onto the charged surface of the latent image carrier to form an electrostatic latent image on the latent image carrier according to the image data; a development device develops the electrostatic latent image with a developer to form a toner image on the latent image carrier; the toner image is transferred from the latent image carrier onto a transfer sheet; and a fixing device applies heat and pressure to the transfer sheet bearing the toner image to fix the toner image on the transfer sheet, thus transferring the toner image onto the transfer sheet.
One common type of developer is a two-component developer, which includes toner and a carrier for carrying the toner. When the developer is agitated and mixed inside the development device, the toner is charged by friction generated between the toner and the carrier and electrostatically attracted to the electrostatic latent image formed on the latent image carrier, thereby forming a toner image.
One known configuration for a development device includes a development member and an agitation member. The agitation member agitates and mixes developer to generate frictional charge between toner and a carrier, and supplies the development member with the developer. The development member supplies the developer to a surface of a latent image carrier carrying an electrostatic latent image to develop the electrostatic latent image into a toner image with the developer.
One known related-art image forming apparatus includes a development device including a paddle for agitating the developer. The paddle includes a rotary shaft and a blade radially extending from the rotary shaft, enabling the paddle to rotate to agitate and mix the developer so as to charge the toner by friction. However, when the paddle has a small surface area, the paddle may not contact all of the developer, thereby causing insufficient dispersion and charging of the toner.
Another known related-art image forming apparatus includes a development device including a screw auger as an agitator. When the amounts involved are not large, such rotating screw auger arrangement can efficiently agitate and mix the components of the developer. However, when a large amount of toner is consumed and supplied, the screw auger may not sufficiently agitate the developer. Consequently, the toner may not be sufficiently dispersed and charged by friction. Insufficiently charged toner may be adhered to a non-image area in which an electrostatic latent image is not formed on a surface of a latent image carrier, or scatter to other peripheral devices, resulting in degradation of image quality.
Toner agitation may be improved by increasing a rotation speed of the paddle or the screw auger. However, doing so may increase a load on a drive system for driving the paddle or the screw auger of the development device, or may cause degradation of toner due to heat of friction generated by agitation.
Obviously, such insufficient charging of toner is undesirable, and accordingly, there is a need for a technology to efficiently agitate developer to supply toner to achieve proper electrical charging without degradation of the developer.